α- or β-hydroxycarboxylic acids are a highly useful class of compounds. They are bifunctional and therefore allow for multiple chemical transformations. The acid group can be converted to a variety of esters, amides, and substituted amides. The hydroxy group along with adjacent hydrogen can be eliminated thus leading to unsaturated compounds. The bifunctional nature of this class also allows polymerization to polyesters, oligomers, and cyclization to lactones or lactides.
Of particular interest is the preparation of commercially important α,β-unsaturated carboxylic acids and their derivatives such as esters, salts or amides of the acrylate and methacrylate families. (Meth)acrylic acid and its derivatives are used as monomers in the manufacture of polymers and copolymers. The formed polymers and copolymers have numerous applications for example in papermaking, solid/liquid separation processes, oil recovery and oil processing, mineral processing, municipal and industrial wastewater treatment, paper, surface coatings, personal care products, adhesives, sealants, absorbents, textile, non-wovens and as rheology modifiers.
Acrylic acid is manufactured by the oxidation of propylene. Acrylic esters are at present manufactured by the esterification of acrylic acid derived from propylene. Preparation of acrylic acid from propane is also known. The most common method of making methacrylic acid is from acetone cyanohydrin. Although propylene is readily available from fossil fuels it would be desirable to synthesize (meth)acrylic acids and esters from renewable resources at equivalent or lower cost.
Acrylamide is generally made by the catalytic hydration of acrylonitrile and substituted acrylamides are made by reacting acrylonitrile with olefins or alcohols under strongly acidic conditions. Other currently practiced processes for manufacture of acrylamides involve a lengthy three-step process starting with a Michael addition to the carbon-carbon double bond which is thermally reversed in the last deprotection step. Thus, a technically simple and economically attractive process from renewable resources for manufacture of (meth)acrylamides and substituted (meth)acrylamides in high yields would also be desirable.
The object of the present invention is to provide an inexpensive process using a starting material that could if desired be derived from wholly renewable resources for the production of these monomers. According to the present invention (meth)acrylic acid and esters are prepared in high yields and selectivity from α- or β-substituted hydroxycarboxylic acids, or precursors of the corresponding α- or β-substituted hydroxycarboxylic acids. The dehydration or dehydration/esterification of the α- or β-hydroxycarboxylic acid may take place in the presence of water and optionally may take place in the presence of a dehydration catalyst and/or esterification catalyst.
(Meth)acrylamides are prepared from α- or β-hydroxycarboxylic acids or derivatives where amidation and dehydration occur in a one or two-step process. Optionally an amidation and/or dehydration catalyst may be used for the reaction.
Furthermore, the (meth)acrylic acid, esters and amides may be made from α- or β-hydroxycarboxylic acids that are derived from biological sources. This could be in the form of α- or β-hydroxycarboxylic acids produced as part of a fermentation process or it may comprise polyhydroxyalkanoates such as polyhydroxypropionate or polyhydroxybutyrate that may be derived from biomass such as microbial cells or plant cells allowing for a most economical route from non-petroleum sources. The polyhydroxyalkanoates can be synthesized by the microbe or plant from sugars such as saccharides, agricultural materials and waste agricultural materials and other biomass.
PCT Application No. WO 03/051813 discusses the treatment of polyhydroxyalkanoates to form esters, amides and alkenoic acid derivatives.
U.S. Publication No. 20020055650 discloses the preparation of methacrylic acids and esters by treating hydroxyisobutyric acid or ester in the presence of an alcohol and solid catalyst.
U.S. Pat. No. 5,250,729 discloses a process for preparation of α,β-unsaturated acids or esters starting from an α- or β-hydroxycarboxylic acid ester. The reaction is carried out in the presence of an acidic dehydration catalyst.
U.S. Pat. No. 2,469,701 describes a process wherein hydracrylic acid is dehydrated at temperatures ranging from 130 to 190° C. in contact with an acid dehydration catalyst.
PCT Application No. WO03/82795 discloses the preparation of α,β-unsaturated carboxylic acid esters from β-hydroxycarboxylic acids or esters in the presence of an alcohol and dehydration catalyst.
U.S. Pat. No. 3,639,466 discloses a process for production of acrylic acid by heating a residue containing hydracrylic acid in the presence of an amine or tertiary phosphine.
U.S. Pat. No. 3,658,895 discloses reacting dilute solutions of acrylic acid with β-hydroxycarboxylic acid in the presence of an acid to form a polyester that is heated to form acrylic acid.
Spanish Patent Application No. ES 515891 discloses preparation of α,β-unsaturated carboxylic acids and/or their esters by dehydration of an α-hydroxycarboxylic acid or its ester in the presence of a solvent, a polymerization inhibitor, and a carrier gas with the aid of Group II, IIIA, IVB, and/or VIII metal sulfate and/or phosphate as catalyst.
German Application No. 3141173 discloses the preparation of α,β-unsaturated acids or their esters by contacting an α-hydroxycarboxamide R1R2C(OH)CONH2 with a solid catalyst, alone or together with H2O, or together with H2O and an aliphatic alcohol, or together with an aliphatic alcohol.
U.S. Pat. No. 3,954,854 discloses recovery of monomeric acrylic acid from a processed crude acrylic acid residue. The residue contains β-acryloxyloxypropionic acid, β-acetoxypropionic acid, hydracrylic acid, dihydracrylic acid and polymeric hydracrylic acid. This residue is treated with a cleavage catalyst at pressure of less than 1 atmosphere and heating to a temperature of 150 to 215° C.
U.S. Pat. No. 2,464,768 describes the preparation of low molecular weight acrylate esters by passing solutions of anhydrous β-hydroxypropionic acid in an excess of alcohol into a mixture of strong acid and copper powder at 130 to 170° C. and distilling out the acrylate ester and water.
European application No. 1,186,592 describes the production of methacryates by passage of solutions of α-hydroxyisobutric acid and an alcohol over a catalyst bed at elevated temperature.
U.S. Pat. No. 2,466,501 describes the preparation of α,β-unsaturated monocarboxylic acid esters by mixing propiolactone and an alcohol passed over an activated carbon catalyst to yield an acrylate ester.
Wislicenus, Justus von Liebig's Ann. Chem, 166, (1873), 1-64 and Wislicenus, Justus von Liebig's Ann Chem, 174, (1874), 285-301 describe the conversion of β-hydroxypropionic acid to acrylic acid. The conversion is achieved via distillation over lead or silver salts to form acrylic acid.
U.S. Pat. No. 2,649,438 describes the formation of acrylamides from β-propiolactone by treatment of the lactone with an amine followed by thermal dehydration. No details are given for this transformation.
Great Britain Publication No. 648,886 describes preparation of unsaturated substituted amides by reacting the β-propiolactone with primary or secondary amines, followed by heating and dehydration to form the substituted acrylamide.
U.S. Pat. No. 4,237,067 discloses a process for manufacture of α,β-unsaturated amides and substituted amides. The starting material is the β-hydroxycarboxylic acid amide. The elimination step requires the presence of an acid or base.
U.S. Pat. No. 5,268,507 describes preparation of amide derivatives of hydroxy acids.
German Application No. 2,819,735 describes the preparation of α,β-unsaturated N-substituted acid amides by heating the appropriate saturated β-hydroxyamide with the appropriate amine, followed by dehydration.
U.S. Pat. No. 2,548,155 describes the formation of hydracrylamide derivatives by treating β-propiolactone with substituted amines.
There is still a need for a process that allows for an efficient, mild and simple preparation of (meth)acrylic acid and its derivatives such as esters, salts and amides prepared from α- or β-hydroxycarboxylic acids or polymers, oligomers, lactides or lactones formed from α- or β-hydroxycarboxylic acids that are optionally derived from renewable resources such as biomass. A simple process is needed whereby the dehydration can be efficiently and effectively carried out in the presence of water under simple, mild reaction conditions. It is further desirable that the ester, acid or amide preparation takes place within the same reactor and virtually no by-products or significant amounts of hazardous waste materials are produced as a result of the reaction.